Ultrahigh-frequency switch tube



Jan 13, 1953 H. HEINS ULTRAHIGH-FREQUENCY SWITCH TUBE Filed Dec. 51, 1948- V I INVENTOR. Harold H 025 ATTORNEY Patented Jan. 13, 1953 ULTRAHIGH-FREQUENCY SWITCH TUBE Harold Heins, Dorchester, Mass, assignor to Sylvania Electric Products Inc., Salem, Mass, a corporation of Massachusetts Application December 31, 1948, Serial No. 68,696

5 Claims. 1

This invention relates to windowed apertures in wave-guides and the like, and particularly to such apertures in transmit-receiving tubes and similar devices, such as are generally used in radar and other ultra high frequency electromagnetic wave transmission tubes for protecting the receiving apparatus while the transmittin pulse occurs. Such tubes are generally gas filled and have one or more resonant circuits with a gap in at least one of them between which a dis charge may flash for operation of the tube, for example, when a wave pulse from the transmitter goes out along the wave guide. Considerable trouble is experienced with such tubes when used at high instantaneous power levels. Ihe characteristics of the tube change and the insulating material of the window deteriorates or reduces the life of the tube.

I have found that this is due toflash-over occurring across the outside of the window, and that this occurs despite the length of gap inside the tube being very much less than the leakage path across the window. The advancing wave front of the pulse reach-es the window before reaching the interior gap, and a high voltage builds up at the window before there is any voltage at the gap.

I find that this may be prevented or inhibited by extending the glass of the window toa considerable distance away from the aperture itself and on the outside of the tube. In some cases, the glass of the window may be extended over the metal support to the walls of the waveguide, although that is not generally necessary. In certain types of prior tubes the glass was sealed in such a way that it extended away from the aperture on the inside of the tube, and with such tubes a reversal of the window is sufiicient to achieve the result.

Other objects, features and advantages will be apparent from the following specification, taken in connection with the accompanying drawing in which:

Fig. 1 is a perspective view of a device according to my invention;

Fig. 2 is a longitudinal section through vice according to my invention.

In the figures, the envelope may comprise for example a waveguide tube 1 of rectangular cross section and fiat end plates 3 generally of larger cross section for a connection, and each having a rectangular window 4 of glass or the like on the outside of the device at the input end. Another window l5 may be placed at the output end, and this output window 15 may have the a deglass sealed to its inside port-ion l6. Extending inside the wave-guide -l and from the shorter walls 5 are small rectangular metal plates 6 and the hollow metal conical pieces 1 extending toward each other from the opposite longer dimension walls between two of the metal plates 6 in a plane transverse to the axis of the wave-guide. The plates 6 and cones 1 together with their metallic connections form a resonant circuit the opposing cones affording discharge gaps, the resonant circuit and cones-constituting a composite resonant circuit and discharge gap struc ture extending across the wave-guide; The

plates 6 extend intothe-wave-guide I through slots. The plates 6 are soldered or welded-to the guide I to form a hermeticalseal.

Some trans-receive tubes may have only one such resonator or may have some other suitable form of resonator, the so-called broad band tubes generally having two .of them, in addition to which the metal plate 3, with its window 4 also forms a resonator, so that in .a tube such as shown in Figure 1, with a window in each end, there are four resonant circuits. The multiplicity of resonant circuits permits the tube to give good response over a broader band-of wave-lengths, in the manner well-known in the art. The resonators are generally spaced one quarter wavelength apart. A keep-alive electrode extends into, but is spaced from one of the cones 1, generally at the resonator nearest the output end of the tube. Electrode I! is joined to a terminal cap 9 carried by glass tube In on flanged metal sleeve II that is in turn sealed to wave-guide l.

The tube may be exhausted through the tubulatio-n l3 extending through one of the walls and sealed hermetically at its outer end. The tube is filled with gas which generally includes a quenching gas, such as water vapor to speed up deionization. The tube may be filled for example with 5 mm. of argon and 3% mm. of water vapor. This pressure is not critical, and is expressed in the usual manner in millimeters of mercury pressure.

A material such as sodium hydroxide may be used to increase the life of the tube in the manner shown in co-pending application Serial 35,905 filed June 29, 1948 by Ezio Thomas Casellini.

My invention is particularly useful as a transnut-receive tube in balanced duplexers and ringtype duplexers, as shown for example in Chapter 8 of the book Microwave Duplexers of the Radiation Laboratory Series, by L. D. Smullin and C. G. Montgomery, and published by the 3 McGraw-Hill Book Company, New York, N. Y. The voltage across the tube window in such circuits reaches very high values.

What I claim is:

l. A high frequency electric discharge tube adapted for mounting in a wave guide structure, said tube being of the type characteristically employing a resonant window, said tube having a gas-filled envelope including a length of hermetically sealed wave guide and a resonant window hermetically sealed to said one end of said length of wave guide, said window having a metal plate in which is provided a central resonant aperture and a hermetically sealed covering of insulating material across said aperture and extending a substantial distance away from said aperture and over the face of said plate on the side thereof away from said length of wave guide and occupying a major part of the diiierence between the area of the aperture and the crosssectional area of the wave guide.

2. A high frequency electric discharge tube of the type characteristically employing a resonant window, said tube having a gas-filled envelope including a length of hermetically sealed rectangular wave guide and a resonant window hermetically sealed across one end of said length of wave guide, said window having a metal plate in which is provided a central resonant aperture and a hermetically sealed covering of insulating material across said aperture and extending over the face of said plate on the side thereof away from said length of wave guide and occupying a major part of the difference in width between said wave guide and said aperture.

3. A high frequency electric discharge tube adapted for mounting in a wave guide structure, said tube being of the type characteristically employing a resonant window, including a gasfilled length of hermetically sealed wave guide, a composite resonant circuit and discharge gap structure extending across said wave guide and spaced one-quarter wave-length away from one end of said length of wave guide, and a resonant window hermetically sealed across said one end of said length of wave guide, said window having a metal plate in which is provided a central resonant aperture and a hermetically sealed covering of; insulating material across said aperture and extending a substantial distance away from said aperture over the face of said plate on the side thereof away from said length of wave guide and occupying a major part of the area difference between the area of the aperture and the crosssectional area of the wave guide.

4. A high frequency electric discharge tube of the type characteristically employing a resonant window, said tube having a gas-filled envelope including a length of hermetically sealed rectangular wave guide and a resonant window hermetically sealed across one end of said length of wave guide, said window havin a, metal plate in which is provided a central resonant aperture and a hermetically sealed covering of insulating material across said aperture and extending over the face of said plate on the side thereof away from said length of wave guide and occupying a major part of the difierence in width between said wave guide and said aperture, and multiple composite resonant circuit and discharge gap structures mutually spaced apart by one-quarter wave-lengths, said window being spaced from the nearest composite resonant circuit and discharge gap structure by a quarter wave-length.

5. A transmit-receive tube adapted for mounting in a wave guide structure, said tube being of the type characteristically employing resonant windows, said tube having a gas-filled envelope including a length of hermetically sealed rectangular wave guide and resonant windows sealed across the ends of said length of wave guide, and plural composite resonant circuit and discharge gap structures extending across said length of wave guide and spaced apart one-quarter wavelength, said windows being spaced one-quarter wave-length from the respective nearest composite resonant circuit and discharge gap structure, one of said composite resonant circuit and discharge gap structures including a keep-alive electrode, one of said windows at the output end of the transmit-receive tube having ametal plate provided with a central aperture and a hermetically sealed covering of insulation material across the aperture and extending over the face of said plate on the inside of the envelope and the other of said windows having a metal plate provided with a central aperture and having a hermetically sealed covering of insulating material across its aperture and extending over the face of its plate on the outside of the envelope facing away from said length of wave guide and occupying a major part of the difference in width between the width of the aperture and the width of the rectangular wave guide.

HAROLD HEINS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,419,903 McCarthy Apr. 29, 1947 2,427,089 Clifford Sept. 9, 194'? 2,496,865 Fiske Feb. 7, 1950 2,499,777 Pound Mar. 7, 1950 

